Underfeed stoker, including a fuel feeder preventing fuel drag-back



Aprxl 17, 1951 .L s. SKELLY 2,549,252

UNDERFEED STOKER, INCLUDING A FUEL FEEDER PREVENTING FUEL DRAG-BACK Filed Nov. 16, 1946 Z Sheets-Sheet l INVENTOR John S. Skelly ATTO RN EY April 17, 1951 2,549,252

J. S. SKELLY UNDERFEED STOKER, ,INCLUDING A FUEL FEEDER PREVENTING FUEL DRAG-BACK 2 Sheets-Sheet 2 Filed NOV. 16, 1946 ATTORNEY Patented Apr. 1.7, i951 UNDRFEED s'roKER, INCLUIING A FUEL FEEDER PREVENTING FUEL DRAG-BACK John Si Skeliy,/`Monongahela, Pak., assigner, by mesne assignments, to Combustion Engineer"-A ing-'Superheatei Inc., a corporation of Dela= Ware Apeliatin Ntvemberie, 154e, sriallv; 710,260 1 claim'. V(o1. 11o- 47) 1 vinvention relates to fuel pusher means ferwunderfeed stokers of the type wherein an orie'n`-top retort and a reciprocating fuel pusher bar is utilized in the general manner disclosed by my U. S. Patent` No. 2,0?1968 of August 4, 1936, for Fuel Burning Device.

Broadly stated, the object of my inventionis to improve the design and better the perforrnance of fuel pusher means for such stokers.

f A more specific object is to raise the effective ness and uniformity with which the stokers reciprocating feeder bar pushes new fuel 'into the fuel-*burning bed at the retorts open top. y

Another object is to reduce the power required to' reciprocate that feeder bar and the pusher I'Jarts"y thereto attached.

' A further object is to lower the pushing sur face needed to advance conveyor-delivered fuel in tothe main body of wretort fuel and thence upwardly into the burning bed.

VAstill Yfurther object is to eliminate drag back of `fuel Yon the feeder bars return stroke and thereby raise the bars fuel displacement efficiency from the some 60% value characteristic of kprior constructions to a new value closely approaching 100%.

4 en additional object is to adapt the pusher parts 4,to various types, sizes and conditions of the. coal or other fuel that is to be burned by the stokerlIn practicing the invention I attain the forem going and other objects andy advantages by mounting the main pusher members on the reciprocating bar sides along the bar portion that passes through the retort end wall beneath the fuel conveyor screw; by so coordinating the member lengths with the span of reciprocating bar travel that the non-pusher ymember ends always stay outside the retort and vhence cannot drag fuel back uponreturn bar travel; by utilizing in proper cases special auxiliary pushers on the bar further within the retort; and by providing means whereby the travel limits of the main pushers may be adjusted without shutting the stoker down.

An illustrative form of my invention is shown by ythe accompanying drawings wherein:

Figure 1 is a view in longitudinal vertical section of a stoker incorporating my inventive improvements;

Figure 2 Vis a section on line 2-21of Figure 1 looking down on the top of my improved pusher parts;

Figure 3 is a section on line 3 3 of Figuretl looking into the pusher faces of the new' side 2 bar members and into the end of the fuel confveyor thereabove; and

Figure 4 is a section on Figure 2s line 4-4 through the feeder bar and one of the auxiliary p'ushers thereon.

y Illustrative' Stoker to be benefited yThe drawings hereof show my improvements applied to an underfeed stoker Whose organization is broadly similar to that disclosed and claimed by my earlier Patent 2,049,668 above identified. YThis showing is merely illustrative and is not to be considered as restrictive; as the description proceeds it will become evident that my improvements also are useful .with uhderfeed stokers of other designs.

In the Stoker construction illustrated, a windy9k organized as infmy earlier patent serves to support the stokers open-top retort I0 within the combustion chamber of a furnace. Coal or other -fuel (not shown) is supplied to the retort from hopper outside the furnace by way of conveyor tube l2 extending through the furnace wall I3. Fuelconveyor screw I4 within the tube is prc'itated by motor I5 (or otherpower means) through reduction gearingl I6, the vscrew speed (relatively slow as one or two R. P.l M.) being selected -by lever if? to provide the desired rate of fuel supply. Entry of conveyor tube I2 into the retorts end wall" I8 is somewhat above the retort vbottom 20 as shown.

lfiilxtendir'ig lengthwise Aof the retort l0 just above bottom wall 20' is the stokers fuel feeder 4 bar 272 whi'oh passes through front end wall I8 below conveyor tube i2. As here shown the bar rests on lendbearing plates 23 and has the nonpacking cross section (best indicated by Figure o taught by my Patent No. 2,433,713 which issued December 30, 1947, from application Serial No. 582,311, lfiled March 12, 1945, for Stoker Pusher Bar.

, Ylteeiproeating,motion.isrimparted to this feeder bar 22, by wobble kearn 2l through ,pusher bar 25 and: connecting plates. In the arrangement shown this wobble' cam is mounted in front of Stoker vhopper H outside the furnace vwhere it is rotated with conveyor VVVscrew le' by motor 1 5 atthe speed (again relatively slow) selected lever l1'. yEach full rotation of the ,cam `produces A.a complet'e'cycle of advance and return bar travel. t y,

. lfIihrough the mediumofpusher. members therei@ attached (end., presently t0 be describe@ the thus-reciprocated Ifeeder bar `.122 progres@ sively advances fuel delivered into the retort by conveyor I4 away from the retorts front end wall I8 and into the main body of retort fuel (not here shown) toward inclined rear wall 30. Such advancement displaces other fuel in that `cody upwardly towards the burning fuel bed at the retorts open top and outwardly upon fire bars 28-29 at the retorts top sides.

Air for supporting fuel combustion passes upwardly from windbox 9 through small passages 32 between fire bars 28-29. Such air may be maintained under pressure in the windbox by a fan (not shown) driven by motor I as taught by my earlier Patent 2,049,668.

All re bars in the two side rows 28-29 may be stationary as illustrated or alternate bars 29 in each row may be arranged to reciprocate toward and from the retort I0 as disclosed by my Patent 2,142,701 of January 3, 1939, for Underfeed Stoker. A dumping grate (not shown) also may be provided at the outer edge of each of these re bar rows.

My improved pusher means My invention provides improved means for causing the reciprocating movement of feeder bar 22 to push fuel in retort I0 away from the end of conveyor tube I2 and into the main body of retort fuel for the purpose of displacing other fuel in that body upwardly towards the retorts open top and into the burning fuel bed thereat as well as onto the rows of re bars 28-29 along the retort sides.

This provision takes the form of main pusher members 36 mounted on the two sides of the pusher bar 22 (and/or on the bar top if desired, but not here so shown) along that portion of the bar which passes through the retorts end wall I8 beneath the conveyor tube I2. These members may satisfactorily take the form of metal blocks shaped as shown; they may be secured to the bar sides in any suitable manner as by means of screws 38 that pass through one of the blocks and the bar to engage with tapped holes in the opposite block as shown; and their lengths are so coordinated with the span of the bar 22s reciprocating travel that their outer or non-pusher ends (closest to connector plates 25) always stay outside retort I0 during the full cycle of advance and return bar travel.

In operation of the stoker the inner or pusher ends (which may satisfactorily be squared as shown) of these blocks 36 within the retort shove fuel thereahead during each advancing travel of the feeder bar 22 and thereby accomplish the desired function of moving fuel away from conveyor tube I2 into the main body of retort fuel. Since the outer or non-pusher block ends never enter the retort, the usual drag back of fuel upon the bars return stroke is eliminated and maximum eciency of fuel displacement is at once realized.

By reason of this absence of drag back I find it sometimes desirable to expose the upper end of conveyor screw I4 for direct discharge of fuel upon the top of the retort fuel bed at the beds front end. In the arrangement shown this exposure is accomplished by a lip-like mouth 4U which inclines upwardly from the top of conveyor tube I2 to an intermediate point in the outwardly inclined fuel retainer 42 at the retorts front end.

For raising the uniformity with which the feeder bars main pusher members 36 advance new fuel into the bed area at retort I0s open top, I sometimes find it further desirable to utilize one or more auxiliary pusher members 44 on the feeder bar 22 closer to the center of the main body of retort fuel. In the form shown such auxiliary members have squared pusher faces, they flank the top and side edges of bar 22, and they are tapered at their opposite edges to minimize fuel drag back.

In order to adapt the improved pusher parts hereof to various types, sizes and conditions of the coal or other fuel that is to be burned by the stoker, I nd it desirable in certain instances to arrange the connecting plates 26 so that the pusher ends of main members 3B can be set to reciprocate closer to or further away from the retort end wall I8 depending upon specific needs. In the arrangement shown such setting is made by moving the attachment of plates 26 from one location to another along the end of feeder bar 22, making use of bar pin 41 and extra plate holes 48. These parts being outside the furnace, adjustment thereof may be effected merely by stopping or declutching motor I5 and without quenching the fire in retort I0.

Advantages aorded Underfeed stokers organized in accordance with my earlier Patent 2,049,668 of 1936 (application therefor filed in 1932) have enjoyed high commercial success in uses such as firing the boilers of heating systems for homes, apartment houses and the like as well as in other applications; this form of stoker uniquely combining the advantages of the screw feed Stoker and of the sliding bottom, pusher and plunger types of stoker without being subject to the disadvantages inherent in these other Stoker types.

Notwithstanding this success, prior art underfeed stokers of the type here considered have been subject to the one significant limitation that my present invention overcomes-namely, drag back of fuel to the retort front on the return feeder bar stroke. My investigations leading to the present improvement have shown that this drag back canv be attributed to the prior art mounting of the first or main pushers on the retort feeder bar with the non pusher end s thereof directly contacting the fuel (as shown in Figures l and 9 of my Patent 2,049,668). The resultant drag back of fuel on the return feeder bar stroke directly opposes the delivery of fuel by conveyor screw I4 and has been so substantial as to make uniform distribution difficult and to result in low displacement efliciency.

These disadvantages are eliminated by my here disclosed improvement of attaching the rst or main pushers 36 to the sides of the feeder bar 22 along that portion of the bar which travels through the retort wall I8 under the discharge end of the conveyor screw I4. With this improvement it requires a very much smaller pushing surface to distribute the fuel from the discharge end of conveyor tube I2, makes it very much easier to secure uniform fuel distribution through the length of the retort IIJ, and reduces the power required to drive the feeder bar 22.

In all prior pusher-type underfeed stokers dating from my early Patent 2,049,668 up to the present, the displacement eiciency has not exceeded about 60%; when equipped with the improved pusher means of my present invention these same underfeed stokers are found to show dsgplacement efficiencies` closely approaching 1 Summary From the foregoing it will be seen that I have improved the design and bettered the performance of underfeed stokers of the type that utilize an open-top retort and a reciprocating fuel feeder bar in the general manner taught by my Patent 2,049,668; that I have raised the effectiveness and uniformity with which such a bar pushes new fuel into the fuel-burning bed at the retorts open top that I have reduced the power required to reciprocate that feeder bar and the pusher parts thereto attached; that I have lowered the pushing surface needed to advance conveyor-delivered fuel into the main body of retort fuel and thence upwardly into the burning bed; that I have eliminated drag back of fuel on the feeder bars return stroke and have thereby raised the bars fuel displacement efliciency from the some 60% characteristic of prior construcend of the retort throughout a major portion of the distance to the rear end, a fuel feed screw delivering fuel substantially horizontally into the forward end of the retort, a reciprocable fuel pusher bar extended horizontally into the retort from the region in front of the front end thereof at an elevation between the bottom wall of the retort and the .feed screw, the pusher bar being Number 6 with the bottom wall of said retort and being of lesser width than and located intermediate the edges of said bottom wall so that fuel introduced by the feed screw rests upon the top of the pusher bar and also upon the edge portions of the bottom wall at the sides of the bar, and fuel pusher elements movable with the pusher bar and projecting laterally therefrom at the bottom wall of the retort and having their bottom surfaces substantially in contact with the bottom wall of said retort and in position to work directly horizontally against fuel at said bottom wall at the sides of the bar, the pusher elements being positioned in the region ofthe front end of the retort and being of sufficient length to locate the working ends thereof within the retort and the other ends thereof in front of the front end of the retort in all positions of reciprocation of said elements with the bar.

JOHN S. SKELLY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Jones Sept. 1, 1896 Hart Aug. 5, 1919 Swindler Feb. 10, 1925 Leach June 24, 1930 Chamberlin Nov. 28, 1933 Beers Feb. 5, 1935 Skelly Aug. 4, 1936 Warg Nov. 24, 1936 Mittendorf Jan. 14, 1941 FOREIGN PATENTS Country Date France Feb. 27, 1939 Number 

